1. Field of the Invention
This invention relates to an aircraft nacelle that incorporates a junction element between a lip and an acoustic attenuation panel.
2. Description of the Related Art
An aircraft propulsion system comprises a nacelle in which a power plant that is connected by means of a mast, for example to the rest of the aircraft, is arranged in an essentially concentric manner.
As illustrated in FIG. 1, the nacelle 10 comprises a pipe 12, a peripheral wall 14, and, at the front, an air intake that is bordered by a lip 16 that connects the pipe 12 and the peripheral wall 14.
The pipe 12 is connected at the rear to the power plant.
In a known manner, the pipe 12 comprises a covering or panel 18 for acoustic treatment that comprises—from the inside to the outside—a reflective layer 20, at least one alveolar structure 22, and at least one acoustically resistive structure 24 that forms the aerodynamic surface of the pipe 12. Advantageously, the lip 16 can also comprise a covering for acoustic treatment.
To reinforce the structure of the nacelle, a front frame 26 is made integral with the lip 16 and extends between the pipe 12 and the peripheral wall 14.
According to one embodiment, to provide the connection between the panel that forms the lip 16 and the panel that forms the peripheral wall 14, the edges of said panels are flattened and then attached by any suitable means against a flange 28 of the front frame 26.
At the junction zone of the lip 16 and the pipe 12, the end of the front frame 26, oriented toward the center of the nacelle, comprises a flange 30 that is oriented toward the rear, and the pipe 12 comprises a flange 32 that is essentially cylindrical. The lip 16 extends toward the rear by an extension 34.
According to an embodiment that is illustrated in FIG. 1, the flange 30 of the front frame is flattened and attached by attachment means 36 against the inside surface of the extension 34 of the lip 16, and the flange 32 of the pipe 12 is also flattened and attached by attachment means 38 against the inside surface of the extension 34 of the lip, with the flange 30 and the flange 32 being arranged side by side.
According to another embodiment that is illustrated in FIG. 2, the extension 34 of the lip 16 is flattened and attached by attachment means 40 against the outside surface of the flange 30 of the front frame, and the flange 32 of the pipe 12 is also flattened and attached by attachment means 42 against the outside surface of the flange 30 of the front frame, with the flange 32 and the extension 34 being arranged side by side.
According to another embodiment that is illustrated in FIG. 3 and in the document FR-2,887,519 for reducing the length of the junction zone in the longitudinal direction, the flange 30 of the front frame is flattened against the inside surface of the extension 34 of the lip 16, and the flange 32 of the pipe 12 is flattened against the inside surface of the flange 30 of the front frame, with the unit being made integral by attachment means 44.
In all of the embodiments mentioned above, the lip, the frame and the pipe are connected directly.
In general, the pipe 12 consists of several panels that are assembled with one another, forming a first essentially rigid subassembly that is essentially cylindrical in shape.
In parallel, the lip 16 and the front frame 26 are assembled in such a way as to form a second essentially rigid subassembly of which an essentially cylindrical peripheral edge that is oriented toward the rear is to be assembled with the pipe 12. Next, these two subassemblies are to be assembled.
To produce this assembly, the two subassemblies are to have dimensions with reduced tolerance intervals at their junction zones so that they can be assembled taking into account certain rigidities therein. However, these reduced tolerance intervals lead to increasing the costs and/or the manufacturing period of these two subassemblies.
As a variant, it is possible to increase the tolerance intervals of each of the subassemblies and to compensate for the dimensional dispersions by blocks inserted between the two subassemblies. However, this solution tends to increase the duration and/or the costs of the assembly.
The document GB-1,427,339 describes an air intake with a lip that comprises panels that form preferred rupture zones on the outside and a pipe with a preferred rupture zone at the rear part. The lip and the pipe are connected by a front frame, with the latter being able to deform in the shape of a cone in case of impact. This front frame does not make possible a relative movement between the inside pipe and the portion of the lip that is arranged in the extension of the inside pipe since these three elements are connected to one another at the same point.